Whale sharks and cetaceans are particularly vulnerable to being encircled by purse seine nets, due to the propensity of tuna to form schools around whale sharks and baleen whales, or for toothed cetaceans to be attracted to the same prey as tunas.

Observers have recorded that 3.2% of purse seine sets are intentionally set on cetaceans or whale sharks, while logsheets only record such targeting as 0.2%. Observer data also demonstrate that all other set types can encircle whale sharks and cetaceans unintentionally, with 60% of observed whale shark interactions occurring in sets classified as ‘unassociated’ (i.e. as free schools of tuna) and 38% of toothed cetacean interactions occurring around anchored FADs.

The paper concludes that: “It is clear that purse seine sets on whale sharks are a combination of both targeted sets and inadvertent capture".